The present invention relates generally to imaging devices. More particularly, the invention is directed to a system for transferring data from an imaging array in a system having high frame rate transfer and windowing capabilities suitable for tracking applications.
Imaging devices are useful in tracking applications for determining the position of an object. For example, it may be desirable to take an image of an object as it moves from one point to another. It is also possible to analyze direction or determined speed of an object and maintain the object in the field of view of a camera.
Infrared charge coupled imaging devices (IR-CCDs) provide low noise and are attractive for tracking applications. Implementation of IR-CCDs in tracking systems has the disadvantage of slow data transfer thereby introducing delay in the tracking loop.
Within the tracking system, transfer of the image from the imaging array is accomplished through the use of a transfer register. The transfer register is approximately the same width as a row of the imaging array. A group of vertical registers are used to transfer an image, one row at a time, from the imaging array into the transfer register. Once a row has been transferred into the transfer register, the transfer register is clocked such that each of the pixel charge packet values are shifted to the next location in the transfer register. The end location of the transfer register is connected to an output port through which data held in the end location may be transmitted. Once the entire row has been output through the output port, a new row is transferred through the vertical registers into the transfer register.
Another aspect of previously known devices for transferring images from an imaging array is that they require the transfer of the entire image stored in the imaging array. Therefore, even if a user requires only a small portion of the image, he user is still required to transfer the entire image. Transfer of the entire image takes valuable time during which the user must wait before a new image can be taken causing delays in the tracking loop. A further problem associated with the present techniques for transferring an image from an imaging array is the loss of charge, known as charge transfer efficiency, as charges are transferred through the vertical registers and the transfer register before being output through the output port. As the rate of data transfer through the system is increased, charge transfer efficiency is reduced.
From the above it is seen that an improved imaging device and associated charge transfer apparatus is desired.